The present invention relates generally to a device and a method for raising sunken objects including small ships and vessels. More particularly, the present invention describes the use of overcooled water to form a layer of ice about the sunken object to temporarily increase its buoyancy.
The problem of recovering sunken objects has been around for hundreds of years. In a typical situation, the sunken object such as a small vessel is pulled up by hoisting cables wrapped about the object. This method has a major disadvantage in that the cables or ropes have to be wrapped first about the object and then the object can be pulled to the surface. At depths greater than divable depths, this procedure can not be easily accomplished since divers are generally needed to position and secure the cables around the object.
Attempts have been made to fill the hull of the vessel with particulate lighter than water and therefore increase the buoyancy of the object so it can be lifted easier. This method is also difficult to achieve as the hull is not always intact and may have openings at different locations making it impossible to contain the filling particulate inside.
Another method known in the prior art is to submerge a hollow chamber next to the object and then attach it to the object. Air is then pumped into the chamber to allow for its lifting together with the object. This method is rather complex and requires a large hollow chamber to be available so a designating recovery ship is usually needed for this operation.
The use of ice is also known in the art of recovery of sunken objects. The advantage is that ice weighs less than water and by attaching a large amount of ice to the sunken object, its buoyancy can be increased. Ice may be formed onsite and therefore easily available. Once on the surface, the ice is simply discarded back into the water.
Several patents of the prior art describe various methods of using ice to recover sunken objects. U.S. Pat. No. 4,690,087 as well as Russian Patents SU 1,785,948; RU 2,009,954; and RU 2,192,985 incorporated herein in their entirety by reference, all describe devices supplying liquid nitrogen or another cryogenic liquid through a network of channels placed about the sunken object to attach that network to the object and form ice about thereof. These methods and devices have limited efficacy since the ice can be formed only up to certain depth about such pipes due to the fact that further increase in depth is limited by the previous layer of ice already formed around each pipe. Therefore, the devices become more complex as more and more pipes are needed both inside and outside the vessel hull. In addition, assembling and subsequent dismantling of the pipe network around the vessel is complicated and requires significant efforts.
The need therefore exists for a simple cryogenic device and method for raising sunken objects without the need for complicated pipe network to be constructed around the object and providing an ability to attach ice of substantial thickness to the sunken object so that it can be easily lifted to the surface.